Let's Make Robots!

Tutorial Trolling

I've seen a few instructable-type tutorials here and there that just look too good to be true.  My favorite was someone trying to convince you that you could run your flat-screen TV by splicing a AAA battery holder into the power cable provided with it.  In any case, I came across a tutorial today (an electronic instrument complete with its own URL and Makerfaire badge) that should have been a straight-up download, upload, hook up some pins and a speaker rig and all I got was one tone, with no reaction to the Inputs.

It got me wondering (and I'm not really ready to say that this is fake-just that it got me thinking about these), have you guys come across this kind of thing often?  People putting up tutorials, walkthroughs, code and tips that just don't work IRL?  What are they getting out of it?  Attention?  Is it really that gratifying to pretend you succeeded where you failed then trying to convince people that "It worked for me-you must just be doing it wrong!"


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attention....and it sorta works for them....they've got a lot of subscribers.

and probably because 60% of watchers of diy videos don't really make anything, they just enjoy someone creating awesome things even though they don't know if it would work or not....Ive read a lot of comments on the Make youtube page, saying that they watch the videos but don't usually make them, for they only enjoy the videos....

On a real great Highlands or Uillean bagpipe or a small pipe, the drones are a constant harmonic tone that sound an octave and two octaves below the tonic tone as long as there is air pressure in the bag. You can hear them really well in "Raigmore" here.

So, I looked a little closer.  I understand most of what is going on now.  However, I'm not sure which is the "latest" version of code.  I was looking at the one linked on the main page, here:


near the bottom under "programming".  It links to the "latest" page on Sourceforge, but the one you put in the link above (linky) appears to be a newer, modified version that has the drone stuff commented out completely.  So what I'm about to say applies to the one I linked to here.

First, the code is crappy.  I'd probably get fired for writing stuff like that.  Anyway, stash the soapbox back under the desk... OK, it uses Direct Digital Synthesis (DDS) to generate the sounds.  Basically that uses an array of sample values for the right wave shape for the instrument, and steps through them faster or slower for the right frequency of each note.  They have written their own capacitive touch sensing routines that measure the time it takes to charge a capacitor on each pin through the built in pullups.  When you touch it, the capacitance goes up so the time to charge goes up and determines you've "pressed" a key.

The Drones ( I still don't know what that means) does an analog read of pin A0, and if it is above a certain level turns on drones, else turns them off.  I'm not sure what is supposed to be connected there, but it is being used as an on/off switch.

Once the proper note(s) are determined, they are set to play.  The playing is done by the ISR routine, which runs every time the timer interrupt fires, 8000 times a second.  At that time, all the notes that are supposed to play get their sample taken out of the DDS array, added together, and sent to the PWM timer, which is used as a Digital to Analog converter.  If you don't have a low pass filter on the output that might be where some of the noise is coming from.  A simple low pass, with maybe a 100 Ohm resistor in series followed by a 1 uF cap to ground  between the pin and the speaker would probably help a lot.

There are a few details I'm still not completely clear on, but I think that covers most of it.  The code you linked to in linky above has some improvements, but overall I think the one I linked is better.  Both could use a lot of work, but hey, if it aint broke...

I hope this helps.  If you have any other specific questions let me know.  

aren't some kind of audio modulation, like a wah wah peddle one might use w/ a guitar?

I wanted to drop you a private message to say thanks, but for some reason I can't. So yeah... Thanks!

Thanks bdk! I got the chanter working actually. There's a lot of noise on it but it's a very cool implementation. The problem was a speaker on the blink. I'd love to hear your ideas though. If you looked at the newest code, he's built drones into it with a sensor on A0-perfect for a conductive foam FSR under the arm!

I don't really have any ideas for improving it.  I had some ideas of why it might not be working.  Basically, they wrote their own capacitive touch sensing routines and I suspected they were kind of flaky.  I was thinking it probably wouldn't work well if it wasn't set up pretty close to how they had done it.  I don't know anything about bagpipes, real or electronic, so that is WAY out of my league.  Glad you got it working.  Would love to hear it play.  Maybe a video?

Would you mind perusing that code again? If I'm reading it right, He talks about A0 (for the "drones") as though it needs a "pressure sensor" but then he polls it like all the other pins. Is that what you're getting from it? linky

I looked briefly at it.  I don't use Arduinos so it's a bit confusing in places.  But, it appears it has some sort of menu option to turn it on or off (or strict mode?).  There is an AnalogRead in there for A0, so it should allow a force sensor, but it looks like it is only using it as an on/off value in the code as is.  I can look through it better when I get more time, probably tomorrow, if you like.

Thanks, I'd appreciate that.  That's about what I'm getting too, but he's using some unfamiliar methods-direct addresses and such that I never really delved into yet.